DESCRIPTION: The studies outlined in this proposal focus on the characterization of EB1 and the exploration of its activities. The proposed studies include: Genetic characterization of EB1: (1) Isolation of human EB1 homologs. Because the available sequences of EST are short, the extent of the homology between genes represented by them and EB1 is not clear. Characterization of these homologs will provide information on similarities and differences among members of this gene family. (2) Isolation of the mouse homolog of EB1. Comparison of predicted amino acid sequences of human and mouse EB1 could indicate important functional domains. Immunological and biochemical characterization of EB1: (1) Characterization of EB1 monoclonal antibodies. Three monoclonal antibodies against EB1 have been obtained. The possibility that they also against EB1 homologs needs to be excluded. Only antibodies specific to EB1 will be useful for the proposed studies. (2) Determination of EB1 expression in cell lines and mouse tissues. Results of this study will provide important information about the where and how much of EB1 expression. (3) Study of the basic biochemical properties of EB1. Experiments will be carried out to elucidate the basic properties of EB1 such as subcellular localization, phosphorylation, complex formation, and the cell cycle regulation of these properties. Functional study of EB1: (1) Mapping the binding regions of EB1 and APC. This information will allow us to generate specific mutants for studying EB1 functions. (2) Study of the regulation of association with APC and EB1. This result can reveal the functional relationship between these two proteins. (3) Investigation of the biological effects of EB1. The effects of increased or decreased expression of EB1 on cell growth will be investigated. These results will provide clues to EB1 functions.